ABSTRACT

A 12-year-old girl was referred to our clinic because of unilateral conjunctivitis not responding to treatment. In the left eye, lower bulbar and tarsal conjunctiva had a polypoidal appearance due to micronodules and there was a subconjunctival nodular mass in the inferior fornix. Systemic examination was unremarkable except for a left preauricular lymphadenopathy. Excision biopsy of the subconjunctival mass revealed a granulomatous inflammation with caseation necrosis, but acid-fast bacilli (AFB) was negative. Fine needle-aspiration biopsy of the preauricular lymph node was performed. In microbiological examination, both AFB and mycobacterial culture were positive. The isolated mycobacteria strains were identified as Mycobacterium tuberculosis complex and full remission was achieved with 6 months of anti-tuberculosis treatment. Although primary tuberculous conjunctivitis is a very rare condition, it should be considered in the differential diagnosis of treatment-resistant unilateral conjunctivitis. For definitive diagnosis, microbiological and histopathological examinations should be performed both in conjunctiva and regional lymph node.

Introduction

Conjunctival tuberculosis is a rare condition. The first definitive conjunctival tuberculosis case was recorded by Koaster in 1873 and numerous cases were reported until the early part of the 20^th century.^#*#ref1#*# In 1912, Eyre¹ reviewed a total of 206 cases with their 24 cases and described the characteristics of conjunctival tuberculosis in detail. Since then, conjunctival involvement has gradually decreased due to advances in the treatment of pulmonary tuberculosis.² In recent decades, only isolated case reports of conjunctival tuberculosis have been published.^{3,4,5,6,7,8,9} Conjunctival involvement is usually through direct inoculation of the organism to the conjunctiva or with contagious spread.^1,2 Conjunctival lesions are generally accompanied by regional lymphadenopathy, but the association with pulmonary tuberculosis is rare.¹ For definitive diagnosis, Mycobacterium tuberculosis organisms must be identified in conjunctival biopsy specimens by direct microscopy or culture.⁹ Histopathological examination and molecular techniques such as polymerase chain reaction (PCR) are also helpful in diagnosis.^3,4

Discussion

Tuberculosis is still an important global health problem. According to the World Health Organization (WHO), in 2011, there were an estimated 8.7 million new cases of tuberculosis globally, equivalent to 125 cases per 100,000 population. About 60% of cases are in the South-East Asia and Western Pacific regions. The African region has 24% of the world’s cases.¹⁰ Although tuberculosis is widespread worldwide, conjunctival involvement is very rare. Most of the cases reported in recent decades have come from endemic regions;^3,4 however, there have been a few case reports from developed countries.^5,6,7,8,9

Turkey is in the WHO European region and has a relatively high tuberculosis incidence rate, 28 cases per 100,000 population.¹⁰ In Turkey, a few cases of primary ocular and orbital tuberculosis were published previously,^11,12,13 but to our knowledge, no cases of primary conjunctival tuberculosis have been reported. Moreover, only 4 cases of conjunctival tuberculosis have been reported from the WHO European region in last 5 decades.^5,6,7,8 Three of the cases were diagnosed with primary conjunctival tuberculosis. Interestingly, these three cases were health professionals (general practitioner, microbiologist, and radiologist) who often encountered Mycobacterium tuberculosis and it was thought that the conjunctival lesions were probably due to direct inoculation of mycobacteria to the conjunctiva.^6,7,8 Our patient was a 12-year-old student and her family screening for tuberculosis is negative. It could not be determined where she came into contact with tuberculosis and how the conjunctival inoculation occurred.

Today, it is very unlikely that tuberculosis would come to mind as a cause of conjunctivitis, even in endemic areas.⁴ Furthermore, variations in the clinical picture complicate the diagnosis. Eyre¹ classified the conjunctival lesions as ulcerative, nodular, hypertrophic granulomatous and pedunculated masses based on the morphological characteristics. In our case, the morphological features of conjunctival lesions resembled nodular and hypertrophic granulomatous types. However, a diagnosis cannot be established on the basis of the lesions’ morphological features. We initially suspected a systemic granulomatous disease such as sarcoidosis, due to the chronic and refractory symptoms. The possibility of tuberculosis conjunctivitis was considered when histopathological examination of the subconjunctival nodule revealed granulomatous inflammation with caseous necrosis.

The definitive diagnosis of conjunctival tuberculosis requires identification of mycobacterium organisms in biopsy specimens by direct microscopy or culture. However, detection of mycobacteria may not be possible in small biopsy samples. In cases in which AFB and culture are negative, PCR amplification of mycobacterial DNA fragments in the tissue or biopsy specimens can be useful in the diagnosis.^4,13,14 In our case, the conjunctival biopsy was negative for AFB. Fortunately, the preauricular lymph node was fluctuant and microbiological examination of lymph node biopsy confirmed the diagnosis of conjunctival tuberculosis.

Although primary tuberculous conjunctivitis is now a very rare entity, it should be considered in the differential diagnosis of unilateral chronic conjunctivitis not responding to treatment. For definitive diagnosis, microbiological and histopathological examinations should be performed both in the conjunctiva and regional lymph nodes.